NEOCENE STRATIGRAPHY. 295 



rock in the line of hills from Point Lobos southeastward 

 past the almshouse to the hills just north of Visitacion 

 Valley on the bay side. This belt includes Bernal 

 Heights. It is not confined to this belt, and usually may 

 be found wherever the serpentine or metamorphic sand- 

 stone occurs. As typical exposures readily accessible 

 from San Francisco might be mentioned exposures in the 

 small hill in the northeast corner of Golden Gate Park ; 

 also in the hill near Strawberry Hill, in the same park, 

 upon which the Prayer Book Cross has been erected. 

 In numerous cuts in the group of hills surrounding the 

 almshouse, and in fact nearly everywhere that it occurs 

 in any quantity, it is much quarried for road material and 

 hence the abundance of excellent exposures. 



Relations and Age. — The evidence, both on the San 

 Francisco peninsula and elsewhere, makes it appear that 

 the phthanite is conformably interbedded with the older 

 sandstone. Mr. F. Leslie Ransome reports this relation 

 to exist just north of the Golden Gate and on Angel Is- 

 land.* It may therefore be considered as of the same 

 age. By a comparison of its radiolarian fauna with that 

 of certain cherts of Europe, it has been thought that the 

 phthanite might be of Jurassic or Cretaceous age.f 



THE METAMORPHIC SANDSTONE. 



Lithology. — In the area studied a metamorphic sand- 

 stone is very abundant in which bedding is visible in only 

 a few places, and then can be followed, as a rule, but a 

 few feet. It is usually light brown or gray in color, 

 rather fine grained, but variable in that respect, breaking 

 along joint planes which seem to form a fine network 

 through it and which are generally stained brown or black. 



* Univ. of Gal., Bull. Dept. of Geol., vol.i, pp. 73-74, and pp. 198, 199. 

 t Univ. of Gal., Bull. Dept. of Geol., vol. i, pp. 237-238. 



